easiest way to determine overlap:

take the adv. intake and exhaust duration. add them.

take the sum, divide by 4.

subtract the LSA from that

multiply by 2.

for example, a comp XE250H is 250/260 adv. 206/212@.050, on a 110 LSA.

so 250+260=510. 510/4=127.5 127.5-110=17.5 17.5*2=35, the cam has 35 degrees of overlap. widen the LSA to 116, and you get 127.5-116=11.5 11.5*2=23, so the cam would have 23 degrees of overlap.

BTW, the overlap numbers I was quoting for the stock cams I was assuming a 114 LSA, since I could find advertised durations for them, but not LSA, and 114 seems reasonable...